鼠标滑过，换背景

 1 ar box = document.getElementById("box");
 2 function fn(liid,bg){  // 封装函数  参数的传递
 3     var obj = document.getElementById(liid);
 4     obj.onmouseover = function(){
 5         box.style.backgroundImage = bg;
 6     }
 7 }
 8 fn("li01","url(images/01big.jpg)"); // 实参
 9 fn("li02","url(images/02big.jpg)");
10 fn("li03","url(images/03big.jpg)");
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原文地址：https://www.cnblogs.com/CoderTony/p/7711250.html